Fix usage of bytes in packaging's bdist_wininst.
Fix usage of bytes in packaging's bdist_wininst.

This is copied from the namesake distutils command; there is no
automated test, so buildbots won’t call for my head this time, but it
should be okay as Python 3 users have tested the distutils command.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator